Genex GXA8/GXD8 Converters

In my continuing quest for better sound, I habitually audition every new digital converter I can get my hands on. When I learned that the new pair of Genex converters featured every standard sample rate known to man, plus DSD conversion, I simply had to try them out.
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In my continuing quest for better sound, I habitually audition every new digital converter I can get my hands on. When I learned that the new pair of Genex converters featured every standard sample rate known to man, plus DSD conversion, I simply had to try them out.
Product PointsApplications: High end recording and editing.

Key Features: Multiple PCM sample rates (from 44.1 kHz to 192 kHz) and DSD; numerous I/O options

Price: $3,345 (GXA8), and $2,995 (GXD8). Expansion I/O cards are $395 to $595 each, with the exception of the DSD output card, which is $1,695 (and the converter must be made ready for it at the factory).

Contact: Genex Audio at 310-828-6667, Web Site.

Plus

+ Versatile

+ Expandable

Minus

- Can't think of any! Well, okay, so they get hot, especially the GXA8.

The Score: These two units receive Dr. Fred's current "Converter du jour" award. A better sounding and more versatile set of converters would be pretty difficult to find.
Features

The twin two-rack-space Genex units, the GXA8 (the A/D box) and the GXD8 (the D/A box) comprise a complete eight-channel conversion set, with eight balanced analog line inputs, eight balanced analog outputs, and eight channels of AES/EBU I/O as well. The closest comparison would be to the Apogee AD-8000, which performs both A/D and D/A functions within the same two-rack-space unit but which, unfortunately, does not convert above a 48 kHz sampling frequency.

Another similarity between the Apogee and Genex units is that both offer the possibility of I/O option card slots in the rear panel; Apogee has four, the Genex boxes have two each. Each of my review units was supplied with AES/EBU and DSD cards since, when operating at the highest sampling rates (176.4 kHz and 192 kHz PCM as well as DSD), the dual-wire protocol effectively halves the number of I/O channels. Thus, the standard built-in AES/EBU connectors support eight channels at sample rates from 44.1 to 96 kHz, but only four at the two highest rates; the extra AES/EBU card gives you the other four. Each of the DSD option cards contains eight BNC connectors, which mate easily (via a breakout cable) with Pyramix's own DVD breakout.

Genex can also supply eight-channel ADAT, TDIF, SDIF2, and Pro Tools I/O cards. The units also feature two bit-splitting modes: Paqrat (same as Apogee's ABS) for PCM, and stereo DSD. Each mode enables one to record on legacy 16-bit MDMs - the former can transmit and receive four channels of 24-bit 44.1 kHz digital audio to and from ADATs and DTRS machines, while the DSD mode splits the stereo DSD signal across all eight MDM tracks.

The front panel controls are both numerous and quite intuitive to use. Unlike the case with some other converters, I never once had to crack the manual to figure something out. There are pushbuttons which toggle the eight vertical LED meters between different peak delay settings, between fine and normal PPM scale, regulate the number of "overs" which will illuminate the over LED, and mute the digital audio. Beneath each meter is a trimpot for adjusting input sensitivity.

One can select different configuration modes for the converters (analog, I/O option slot 1, slot 2, and DSD), and adjust the clock's sensitivity in "lock mode" between wide and precision. The AES/EBU outputs can toggle between single, dual, or quad-wire, the clock source can alternate between internal crystal, external word clock, or the audio from either of the option cards. The sample rate and bit depth can also be adjusted via front panel pushbuttons.

The analog I/O has a very strong preference for balanced signals. In fact, the review sample was practically unusable with the direct outs from my Crane Song Spider mixer, as that unit produced a bit of DC offset which interacted with the DSD input amplifier (PCM was okay). Hastily-wired little adapter plugs with internal 70-ohm resistors reduced the offset. Since the review unit was from an early build, Genex informed me that later units' DSD inputs will not be nearly as "fussy." The balanced ouputs can be unbalanced by simply leaving one leg unconnected; shorting the unused pin to ground is not recommended.

In Use

Over a period of several months, I have used these converters at all three sample rate levels - standard, double, and quadruple frequency and, of course, in DSD mode as well. I have used them on every recording I have made during the first half of 2002, and even built my new Pyramix DAW around them. Thus, I feel confident in being able to describe their sound - or, should I say, sounds.

Used as PCM converters, they sounded just as I would expect from units at this price level; clear, sharply chiseled and better and airier as the sampling frequency ascended. They also had a particularly "big" sound that is hard to describe. One might call it "ballsy," or almost larger than life. They flattered just about all sound sources I fed them; they were the strongest-sounding 44.1 kHz converters I have ever used (as opposed to warm, or mellow - like Apogee's), but their personality was always pleasing to my ears. I would rate them right up at the top of the heap.

At a big bucks brass band recording session I did for Dorian in early June, their sound at 176.4 kHz was clearly the best I had ever captured of that group. Unfortunately, in DSD mode, I had trouble getting all my six mic channels reliably into my brand new Merging Pyramix DAW (which was the session recorder) due to clocking issues between the Genex and Merging hardware, but that really did not matter because I preferred the Genex's 176.4 kHz PCM sound to DSD for those particular brass instruments anyway.

So what exactly did Genex's DSD conversion sound like? Well, think analog. Think mellow, laid-back, relaxed, and a tidge heavy. It is easy to connect Genex's GXA8 and GXD8 converters back to back, and switch between 176.4 kHz and DSD while listening to a analog source, so I did many A-B tests this way. Whereas Genex's high resolution PCM conversion sounded etched, sharp, detailed, big, and ballsy, its DSD process sounded, well, a little heavier and duller; almost as if the spectral energy had been moved down half an octave (or a little like the "tilt" equalization control on some vintage British electronics.)

On some sources, this DSD "effect" was flattering and, in fact, was preferable to the lighter detailed and etched treatment imparted by Genex's PCM conversion. But on some of the other sources I tested during the review period, it made a female vocalist sound a little too "chesty," and some of the ultimate air was lost on, say, brushes and cymbals, or even harpsichord.

Please bear in mind that, in actuality, these differences were very slight; I have just worked very hard to come up with appropriate language to describe them. I also found it fascinating that, for this - my second audition of DSD conversion (the first was dCS 904 and 954 converters I reviewed in PAR 12/00), my subjective evaluations of DSD were similar in each case.

One should also remember that some of us have been recording via PCM since the early 80s, and have evolved ancillary equipment and techniques to make the most of the PCM "sound." I feel I could easily learn to do the same thing if I were "forced" to use only DSD conversion. DSD's "relaxed" and mellow (as opposed to the typical "aggressive" and "chiseled" PCM) characteristics are, arguably, an easier sound to work with than PCM.

I can certainly understand why certain audiophile engineers seem to prefer DSD these days. But just as I had to change many of my recording techniques and front-end equipment back in the eighties in order to make my PCM recordings sound "more like the source," I would definitely have to perform an analogous process were I to make the switch to DSD. The two conversion techniques definitely have different sounds (as also does analog recording on magnetic tape); not one of the three is the proverbial "straight wire with delay."

Summary

The audition period for these two superior pieces of Genex gear was definitely an educational opportunity for me. I have concluded that the world of professional audio recording now has three different - and equally valid - sound storage universes: analog, PCM, and DSD. Each has its own strengths and weaknesses and all will, I feel, be used alternatively in the future. The Genex GXA8 and GXD8 converters are presently unique in the marketplace since they permit one to enjoy the best characteristics of two of these three universes. Buy these converters, and then add a high-end Studer or Ampex analog tape recorder to your studio, and you will have all three. I should know; that is what I am going to do!

REVIEW SETUP

Crane Song Spider mixer; D.W. Fearn VT-2, Manley Mic/EQ-500, Millennia Media M-2B vacuum tube mic preamps; Neumann M 50, SM 69, U 47, M 249, AKG C 24, Royer SF 12A microphones, Merging Technologies Pyramix DAW; Weiss DAC1 digital audio converter; Éclair Engineering custom vacuum tube monitoring console; IMF Electronics SACM transmission line monitors driven by McIntosh MI-200 vacuum tube amplifiers, Manley Tannoy loudspeakers driven by VTL MB-300 vacuum tube amplifiers, Dynaudio BM6A active loudspeakers.